The invention relates to a test apparatus for the simultaneous loading of a test sample with longitudinal forces and with torque moments. The test apparatus comprises a machine frame, e.g., a two post machine frame, a hydraulic loading cylinder attached to the machine frame for producing the longitudinal forces and a hydraulic rotating piston cylinder arrangement for producing the torque or torque moment.
Testing devices for the simultaneous loading of a test sample with longitudinal forces and torque moments are known which have so-called "rotating cylinders" attached to the piston rod of said hydraulic loading cylinder. So-called "rotating cylinders" operate in accordance with the vane or wing principle. A rotary piston is rotatably mounted in a sealed manner within a casing and is provided with one or two inwardly directed wings or lands. When a pressure medium is fed into the chambers formed by the housing and the rotary piston, the rotary piston may be rotated approximately .+-.150.degree. or .+-.60.degree. from its central position relative to the casing. When the casing is immovably secured, torque may thus be produced by the rotary piston. Such torque may, for example, be transmitted to a test sample. The combination of a longitudinal loading cylinder with a rotating piston cylinder device thus permits the simultaneous production of longitudinal forces and torque moments and a corresponding loading of the test samples.
The rotating cylinder of a known arrangement is attached to the piston rod of the longitudinal loading cylinder and is moved along with the longitudinal movements of the longitudinal loading piston cylinder. The piston rods of the longitudinal loading cylinder and of the rotating piston cylinder are securely fastened to each other. The piston rods and the pistons perform the longitudinal and rotary movement together. The housing of the rotating piston cylinder is guided longitudinally and is supported in the direction of rotation on the stationary portion of the testing apparatus so that the torque may be transmitted to the test sample which is connected to the rotary piston. The longitudinal force is transmitted to the test sample through the rotary piston.
The rotating cylinder with its supply lines for the pressure medium is subjected to heavy loading during larger longitudinal movements and at higher test frequencies. In addition, undesired inertial forces and considerable frictional force occur in the longitudinal guide means required for the rotating cylinder. Another disadvantage is seen in that circumferential play may be eliminated only with difficulty. The loading of the test sample and the test results respectively may be influenced by these factors.